During photorespiration RuBisCO acts as

Options

A. Oxygenase
B. Carboxylase
C. Transaminase
D. Reductase

Answer

### Step-by-Step Solution

1. **Understanding Photorespiration**:
- Photorespiration is a process that occurs in plants, particularly during the Calvin cycle. It is considered a wasteful pathway because it can lead to the loss of fixed carbon and energy.

2. **Role of RuBisCO**:
- RuBisCO stands for ribulose-1,5-bisphosphate carboxylase/oxygenase. It is an enzyme that plays a crucial role in the Calvin cycle, facilitating the fixation of carbon dioxide.

3. **Enzymatic Activity of RuBisCO**:
- RuBisCO can catalyze two different reactions:
- It can act as a carboxylase, fixing carbon dioxide during photosynthesis.
- It can also act as an oxygenase, where it reacts with oxygen instead of carbon dioxide, leading to photorespiration.

4. **Identifying the Correct Option**:
- The question asks how RuBisCO acts during photorespiration. Since photorespiration involves RuBisCO reacting with oxygen, it is acting as an oxygenase in this context.
- Therefore, the correct answer is **oxygenase**.

5. **Conclusion**:
- During photorespiration, RuBisCO acts as an oxygenase.

### Final Answer
During photorespiration, RuBisCO acts as an **oxygenase**.